1. Field of the Invention
The present invention relates to an active energy ray-curable resin composition capable of imparting scratch resistance, antistatic property and anti-staining property to surfaces of, for example, functional optical films such as anti-reflection films and near-infrared ray absorbing films on surfaces of optical information media such as read-only optical disks, optical recording disks and magneto-optical recording disks, and liquid crystal displays and plasma displays. Furthermore, the present invention relates to a laminate having a hard coat layer formed from the active energy ray-curable resin composition on a substrate.
2. Disclosure of the Related Art
Recently, optical recording devices, which are capable of recording a large capacity of data at a high density and quickly recording and reproducing data, have come to attract attention with development of multimedia. Such optical recording devices include devices which reproduce read-only disks such as CDs and laser disks, in which information is stamped thereon during the disk production and which are capable of only reproducing information; devices which record and reproduce write-once disks such as a CD-R, which are capable of recording only once; and devices which reproduce and record rewritable disks, in which data can be rewritten and erased any number of times by using the magneto-optical recording system or the phase-change recording system. In such optical recording devices, reproducing and recording of data are performed by the use of a light spot obtained by focusing laser light to the diffraction limit with a lens.
In order to record information at a higher density, in other words, to form smaller bit patterns on an optical information medium, it is necessary to make a laser light spot smaller. There are two possible methods for making a size of a light spot smaller, namely, a method of reducing the laser light wavelength (λ) and a method of increasing the numerical aperture (NA) of the lens. While the wavelength of the laser light currently used for optical disks is mainly from about 780 nm to about 650 nm, use of blue laser light or the like having further shorter wavelength have increasingly been investigated.
As to the system which uses blue laser light, the minimum bit length has been reduced to about 0.14 μm by adjusting the wavelength of the light source to 405 nm, the NA to 0.85, and the track pitch to 0.32 μm. Thereby, blu-ray disks having a recording capacity as large as 4 times or more that of a DVD have been commercialized. However, when the wavelength of a light source is reduced or the NA of an objective lens is increased, the focal length of light becomes shorter. A lens having a higher NA produces blur or aberration more easily. Furthermore, it becomes severer to control of the amount of substrate distortion (tilt) with which the surface of an optical disk inclines from the right angle relative to the optical axis, or of the unevenness in thickness of optical disks.
Therefore, a data is recorded or reproduced by irradiating laser light converged through a lens having a specific numerical aperture to a recording layer through a 1.2 mm thick polycarbonate substrate surface in conventional CDs, or through a 0.6 mm thick substrate in DVDs having two 0.6 mm thick polycarbonate substrates laminated. Conversely, in the case of using blue laser light, a system is used in which a recording layer is formed on a polycarbonate substrate and further a thin-film cover layer of about 0.1 mm in thickness is formed thereon, and data are read by irradiating blue laser light to the thin-film cover layer surface.
The thin-film cover layer is composed of a light transmitting layer which protects the recording layer directly and a hard coat layer for protecting the whole disk surface. The light transmitting layer is formed by a method in which an active energy ray-curable resin is applied onto the surface of the recording layer to spread uniformly by a spin coating method or the like, or a method in which films are laminated. A hard coat layer is formed by applying an active energy ray-curable resin composition and then spreading it uniformly by a spin coating method or the like. While a hard coat layer is formed for the purpose of preventing scratching or adhering of dust or stain such as fingerprint, which will cause errors during recording and reproducing, these properties are extremely important particularly in use of blue laser light.
On the other hand, a hard coat layer which is formed on a surface of a functional optical film to be used for the surface of a liquid crystal or plasma display is required to have excellent property in, for example, hardness, transparency, antistatic property for preventing dust due to static electricity from adhering, and the property of preventing adhesion of stains such as fingerprint, depending on its intended use. Various components are used depending upon the property. These functional optical films are formed in a single layer structure or a multilayer structure on a transparent film of a resin such as polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA) or triacetyl cellulose (TAC). Moreover, such films are required to be transparent and uniform films free of birefringence because of their properties.
Conventionally, fluorine monomers have been added to a compound having an active energy ray-curable unsaturated bond for the purpose of preventing stains such as fingerprint from adhering to a hard coat layer. In addition, in order to prevent scratching or dust adhesion, addition of silica fine particles or fine particles of a metal oxide such as tin oxide-doped indium oxide (ITO) or tin oxide-doped antimony oxide (ATO), addition of fine particles obtained by modifying the surface of such fine particles with a hydrolyzable silane compound, and addition of a quaternary ammonium salt have been performed.
Patent Document 1: JP-A-2003-196883
Patent Document 2: JP-A-2005-126453
Patent Document 3: Japanese Patent No. 2506065